Blocked Intake Vent on Water Heater

I was hoping to get input on a unique water heater problem that we discovered in our home today. We moved into our home 4 months ago and it was a new construction. I've always thought the water was way too hot for the setting we had it on, and even though we kept turning it down it didn't seem to help. We finally had the builder send out their plumber to troubleshoot. The following is my understanding of the problem based on the explanation from the plumber today. I know very little about the functionality of our water heater (shame on me), so forgive me if any of the following sounds illogical:
We have an AO Smith Power Vented gas water heater. It turns out that someone (most likely the water heater installer) left a plastic bag containing some spare installation kit parts for the water heater on top of the tank - right next to the air intake for the blower (marked Blower Dilution Air Inlet on the manual). When the blower motor kicked on, it was sucking the plastic bag up against the intake vent. Then after about 5 min, (during which time the entire housing around the blower motor assembly got extremely hot- too hot to touch) the air pressure sensor would trip and turn the whole water heater off. So, basically it was continually short cycling over and over. This was causing small amts of hot water to be generated, but the entire tank didn't heat correctly since it was getting kicked off over and over. So, the hot water would rise to the top and water would get extremely hot near the top. My question...is it likely that this continual short cycling of the blower motor for four months likely did damage to the motor? My main concern is that the motor and housing got VERY hot for such a prolonged period of time. I looked back at pictures from our final inspection 4 months ago and verified the bag was there all along (yes, shame on me for not educating myself on the wonderful workings of our water heater - and also shame on the inspector, and installer). The plumber said I shouldn't worry,but he isn't exactly an unbiased opinion. The builder is responsible for repair/replacement. I'm wondering if and what parts might need to be replaced. Thanks in advance for your opinions!

I have a Richmond power vented model and on mine the blower assembly is just attached with sheet metal screws to the top of the tank. So if you undid the clamp to the vent pipe and took screws out the blower unit could be replaced. On my water heater the intake hangs over the side of the tank, not sure how a bag could get close enough to get sucked in. I would assume you have a 7 year parts waranty, but only a 1 year labor. (not sure what my warranty is) I'm amazed you could go 4 months with something like that going on and still have enough hot water to keep you satisfied. Hope some pro comes along and says why your water would be so hot. Would the heat be from the exhaust gas not being exhausted very well, or from the heat of the blower motor....interesting.